1. Field of the Invention
This invention relates to security screens for use in banks, savings and loan premises, building society offices and the like, and in particular relates to an anti-jamming device for such screens.
2. Description of the Prior Art
U.S. Pat. Nos. 4,748,914 and 4,831,939 describe security screens o the indicated type. Such screens are adapted to rapidly ascend from counters when a robbery is detected, thus screening staff and currency from the robbers. There is a concern that such screens may jam, rendering them ineffective.
One existing approach to counteract security screen jamming is to use a collapsible bulkhead. In such an arrangement the bulkhead is constructed to collapse when a screen is jammed by having something placed over it.
Whilst this approach is effective, there are a number of disadvantages. Once the bulkhead has collapsed, a major rebuild must be undertaken before the premises are able to operate normally. Furthermore, the aesthetic design of the bulkhead is greatly limited. In addition, when an existing security screen system is upgraded, the cost of a collapsible bulkhead is prohibitive.
Finally, a collapsible section of at least the reach of the screen is required over and above the lower level of the bulkhead. This amount of room is rarely available.
Another prior manner of overcoming screen jamming consists of a flap covering the opening from which the screen emerges, the flap is hinged on the front edge. When the screen is activated the flap flips forward theoretically knocking away the jamming device if it falls within a length that will be hit by the flap. If it is too long the flap will fail to open, if it is too short the flap will miss completely.